Final answer:
To prove that the x national number and abc are all different integers, we can use a proof by contradiction.
Step-by-step explanation:
To prove that the x national number and abc are all different integers, we need to show that they cannot have the same value. We can prove this by contradiction. Let's assume that x and abc are the same.
Since x is an integer, it can have any value. Let's say x = 5.
Now, since abc is also an integer but different from x, it cannot have the same value. Let's say abc = 5. But this contradicts our assumption that x and abc are the same.
Therefore, we can conclude that x and abc must be different integers.